Networked automation devices, as needed for Industry 4.0 or Cyber Physical Production Systems, demand for new programming languages like the one defined in the IEC 61499 standard. IEC 61499 was originally released in 2005. Since then, different runtime environmentsacademic and commercial-surfaced: They partly differ in their execution semantics and behavior, and in the features they offer, e.g. Multitasking, Real-time performance, or Dynamic Reconfiguration. Users who want to apply this standard to their problem have to choose the right tool. This paper compares a selection of IEC 61499 runtime environments and outlines topics for further research.